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Updated: Jun 27, 2026

Heterogeneous Removal of Water-Soluble Ruthenium Olefin Metathesis Catalyst from Aqueous Media Via Host-Guest Interaction
Published on: August 23, 2018
A Mesopore-Confined and Graphene Oxide-Localized Ruthenium Catalyst Increases Rates of Mid-Chain Polyolefin
Kajol Tonk1,2, Simin Sun1,2, Olajide H Bamidele3
1Department of Chemistry, Iowa State University, Ames, Iowa50011, United States.
Abstract:
A catalyst architecture with mesoporous silica coating Ru nanoparticles on reduced graphene oxide (mSiO2/Ru/rGO) localizes the 2 nm Ru solely at the closed bottoms of 2.9 nm diameter mesopores. mSiO2/Ru/rGO catalyzes the rapid, selective hydrogenolysis of polyolefins at wax formation rates (νwax) up to 1700 gwax·gRu-1·h-1 and a turnover frequency (TOF) for C-C bond cleavage of 130 ± 8 min-1. The νwax and TOF for mSiO2/Ru/rGO are 23× and 16× those of nonporous Ru/rGO, respectively, indicating that faster chain cleavage is also more selective inside mesopores. The methane yield from mSiO2/Ru/rGO is ca. 30% of the value obtained from Ru/rGO. Methane decreases, and wax selectivity improves with narrow-pore (2.3 nm) mSiO2/Ru/rGO. The reaction rate decreases at lower and higher H2 pressures from its maximum at 37 bar. Log(TOF)-log(PH2) plots reveal rates ∝ [PH2]2.8 or [PH2]-2.0 in the lower or higher pressure ranges, respectively. Corresponding plots for Ru/C give rates ∝ [PH2]1 or [PH2]-2.4. Ru is hydrocarbon-covered at low pressure; thus, the higher H2 order for mSiO2/Ru/rGO indicates that mesopores increase the density of cleavable unsaturated moieties on the Ru surface. The lower H2 order on Ru/C implies a lower density of cleavable groups because saturated segments occupy a larger fraction of the Ru surface. Higher surface occupancy by the hydrocarbon reactant correlates with more methane formation. Therefore, pore confinement, narrower pore diameter in mSiO2/Ru/rGO, or higher H2 pressure leads to lower methane yields. Ru nanoparticles in mSiO2/Ru/rGO maintain equivalent activity and selectivity over five recycling tests.
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